1. Technical Field of the Invention
The present invention relates to frequency re-use structures, and more particularly, to a frequency re-use structure, including seven cell clusters that substantially eliminates adjacent channel interference.
2. Description of Related Art
Frequency re-use patterns are cell-based structures by which the frequency channels within a cellular radio system are assigned. The most basic unit of any frequency re-use pattern is a cell. To each cell in a frequency re-use pattern are assigned a number of frequency channels. A group of cells associated together are referred to as a cluster. A cluster contains all of the frequency channels available to a particular cellular radio system. Groups of clusters are then used to provide a cellular coverage over a specific area for a cellular system. The association of all frequency channels within a single cluster enables the re-use of the frequency channels throughout the cellular system.
The clusters are structured and frequencies within the clusters assigned to increase the re-use distance and limit co-channel and adjacent channel interferences. Co-channel interference consists of interference caused between uses of the same frequency within two different cell clusters. Adjacent channel interference is caused by interference between adjacent frequency channels within the same cluster or within two different clusters. In order to reduce interference within the cellular system, both co-channel and adjacent channel interference must be minimized. Competing with these requirements is the need for increased system capacity. In general, the smaller number of cells used in a cluster within a mobile radio system, the higher the capacity of the system and the lower the co-channel re-use distance. A smaller co-channel re-use distance, of course, increases co-channel interference.
Frequency re-use patterns have been extensively studied in the cellular industry. Frequency re-use patterns minimizing adjacent channel interference have been proposed for cell clusters of greater than nine cells in size. However, claims have been made in existing studies, that adjacent channel interference may not be avoided when the number of cells in a cluster is less than nine. Existing frequency re-use patterns using less than nine cells, all suffer from the problem of adjacent channel interference. A system which enabled the use of clusters including less than nine cells with enhance channel capacity, provided good co-channel interference characteristics and substantially eliminated adjacent channel interference problems would greatly benefit users and providers of cellular telephone services.